Abstract
We analyze the far-infrared (FIR) properties of ∼5000 star-forming galaxies at
z
< 4.5, drawn from the deepest, super-deblended catalogs in the GOODS-N and COSMOS fields. We develop a novel ...panchromatic spectral energy distribution fitting algorithm,
Stardust
, that models the emission from stars, active galactic nuclei (AGNs), and infrared dust emission, without relying on energy balance assumptions. Our code provides robust estimates of the UV−optical and FIR physical parameters, such as the stellar mass (
M
*
), dust mass (
M
dust
), infrared luminosities (
L
IR
) arising from AGN and star formation activity, and the average intensity of the interstellar radiation field (〈
U
〉). Through a set of simulations we quantify the completeness of our data in terms of
M
dust
,
L
IR
, and 〈
U
〉 and subsequently characterize the distribution and evolution of these parameters with redshift. We focus on the dust-to-stellar mass ratio (
f
dust
), which we parameterize as a function of cosmic age, stellar mass, and specific star formation rate. The
f
dust
is found to increase by a factor of 10 from
z
= 0 to
z
= 2 and appears to remain flat at higher
z
, mirroring the evolution of the gas fraction. We also find a growing fraction of warm to cold dust with increasing distance from the main sequence, indicative of more intense interstellar radiation fields, higher star formation efficiencies, and more compact star-forming regions for starburst galaxies. Finally, we construct the dust mass functions (DMFs) of star-forming galaxies up to
z
= 1 by transforming the stellar mass function to DMF through the scaling relations derived here. The evolution of
f
dust
and the recovered DMFs are in good agreement with the theoretical predictions of the Horizon-AGN and IllustrisTNG simulations.
Abstract
Until now, our knowledge of the extragalactic universe at mid-infrared (mid-IR) wavelengths (>5
μ
m) was limited to rare active galactic nuclei and the brightest normal galaxies up to
z
∼ 3. ...The advent of JWST with its Mid-Infrared Instrument (MIRI) will revolutionize the ability of the mid-IR regime as a key wavelength domain to probe the high-
z
universe. In this work we present a first study of JWST MIRI 7.7
μ
m sources selected with >3
σ
significance from the lensing cluster field SMACS J0723.3-7327. We model their spectral energy distribution (SED) fitting with 13 JWST and Hubble Space Telescope broad bands, in order to obtain photometric redshifts and derived physical parameters for all these sources. We find that this 7.7
μ
m galaxy sample is mainly composed of normal galaxies up to
z
= 4 and has a tail of about 2% of sources at higher redshifts to
z
≈ 9–10. The vast majority of our galaxies have 3.6–7.7 < 0 colors and very few of them need high dust extinction values (
A
V
= 3–6 mag) for their SED fitting. The resulting lensing-corrected stellar masses span the range 10
7
–10
11
M
⊙
. Overall, our results clearly show that the first MIRI 7.7
μ
m observations of deep fields are already useful to probe the high-redshift universe and suggest that the deeper 7.7
μ
m observations to be available very soon will open up, for the first time, the epoch of reionization at mid-IR wavelengths.
Abstract
Recent data from the James Webb Space Telescope allow a first glimpse of galaxies at
z
≳ 11. The most successful tool for identifying ultra-high-redshift candidates and inferring their ...properties is photometric template fitting. However, current methods rely on templates derived from much lower-redshift conditions, including stellar populations older than the age of the Universe at
z
> 12, a stellar initial mass function that is physically disallowed at
z
> 6, and weaker emission lines than currently observed at
z
> 7.5. Here, two sets of synthetic templates, optimized for the expected astrophysics of galaxies at 8 <
z
< 12 and
z
> 12, are developed and used to fit three galaxies at
z
> 12 from the SMACS0723 field. Using these improved templates, quantitative estimates are produced of the bias in inferred properties from JWST observations at
z
> 8 due to these effects. The best-fit redshifts are similar to those found with previous template sets, but the inferred stellar masses drop by as much as 1–1.6 dex, such that stellar masses are no longer seemingly inconsistent with ΛCDM. The two new template sets are released in formats compatible with
EAZY
and
LePhare
.
One of the most significant climate change impacts on arctic urban landscapes is the warming and degradation of permafrost, which negatively affects the structural integrity of infrastructure. We ...estimate potential changes in stability of Russian urban infrastructure built on permafrost in response to the projected climatic changes provided by six preselected General Circulation Models (GCMs) participated in the most recent Climate Model Inter-comparison Project (CMIP5). The analysis was conducted for the entire extent of the Russian permafrost-affected area. According to our analysis a significant (at least 25%) climate-induced reduction in the urban infrastructure stability throughout the Russian permafrost region should be expected by the mid-21st century. However, the high uncertainty, resulting from the GCM-produced climate projections, prohibits definitive conclusion about the rate and magnitude of potential climate impacts on permafrost infrastructure. Results presented in this paper can serve as guidelines for developing adequate adaptation and mitigation strategy for Russian northern cities.
ABSTRACT
We study the interstellar medium (ISM) properties as a function of the molecular gas size for 77 infrared-selected galaxies at z ∼ 1.3, having stellar masses 109.4 ≲ M⋆ ≲ 1012.0 M⊙ and star ...formation rates 12 ≲ SFRFIR ≲ 1000 M⊙ yr−1. Molecular gas sizes are measured on ALMA images that combine CO(2-1), CO(5-4), and underlying continuum observations, and include CO(4-3), CO(7-6) + CI(3P2 − 3P1), CI(3P1 − 3P0) observations for a subset of the sample. The $\gtrsim $46 per cent of our galaxies have a compact molecular gas reservoir, and lie below the optical discs mass–size relation. Compact galaxies on and above the main sequence have higher CO excitation and star formation efficiency than galaxies with extended molecular gas reservoirs, as traced by CO(5-4)/CO(2-1) and CO(2-1)/LIR, SF ratios. Average CO + CI spectral line energy distributions indicate higher excitation in compacts relative to extended sources. Using CO(2-1) and dust masses as molecular gas mass tracers, and conversion factors tailored to their ISM conditions, we measure lower gas fractions in compact main-sequence galaxies compared to extended sources. We suggest that the submillimetre compactness, defined as the ratio between the molecular gas and the stellar size, is an unavoidable information to be used with the main sequence offset to describe the ISM properties of galaxies, at least above M⋆ ≥ 1010.6 M⊙, where our observations fully probe the main sequence scatter. Our results are consistent with mergers driving the gas in the nuclear regions, enhancing the CO excitation and star formation efficiency. Compact main-sequence galaxies are consistent with being an early post-starburst population following a merger-driven starburst episode, stressing the important role of mergers in the evolution of massive galaxies.
We report Atacama Large Millimeter Array observations of the neutral atomic carbon transitions C i and multiple CO lines in a sample of ∼30 main-sequence galaxies at , including novel information on ...C i and CO for 7 of such normal objects. We complement our observations with a collection of >200 galaxies with coverage of similar transitions, spanning the z = 0-4 redshift interval and a variety of ambient conditions from local to high-redshift starbursts. We find systematic variations in the C i/IR and C i/high-Jupper (Jupper = 7) CO luminosity ratios among the various samples. We interpret these differences as increased dense molecular gas fractions and star formation efficiencies in the strongest high-redshift starbursts with respect to normal main-sequence galaxies. We further report constant / ratios across the galaxy populations and redshifts, suggesting that gas temperatures Texc traced by C i do not strongly vary. We find only a mild correlation with Tdust and that, generally, Texc Tdust. We fit the line ratios with classical photodissociation region models, retrieving consistently larger densities and intensities of the UV radiation fields in submillimeter galaxies than in main-sequence and local objects. However, these simple models fall short in representing the complexity of a multiphase interstellar medium and should be treated with caution. Finally, we compare our observations with the Santa Cruz semi-analytical model of galaxy evolution, recently extended to simulate submillimeter emission. While we confirm the success in reproducing the CO lines, we find systematically larger C i luminosities at fixed IR luminosity than predicted theoretically. This highlights the necessity of improving our understanding of the mechanisms regulating the C i emission on galactic scales. We release our data compilation to the community.
Abstract
We present the results of a systematic search for candidate quiescent galaxies in the distant universe in 11 JWST fields with publicly available observations collected during the first 3 ...months of operations and covering an effective sky area of ∼145 arcmin
2
. We homogeneously reduce the new JWST data and combine them with existing observations from the Hubble Space Telescope. We select a robust sample of ∼80 candidate quiescent and quenching galaxies at 3 <
z
< 5 using two methods: (1) based on their rest-frame
UVJ
colors, and (2) a novel quantitative approach based on Gaussian mixture modeling of the near-UV −
U
,
U
−
V
, and
V
−
J
rest-frame color space, which is more sensitive to recently quenched objects. We measure comoving number densities of massive (
M
⋆
≥ 10
10.6
M
⊙
) quiescent galaxies consistent with previous estimates relying on ground-based observations, after homogenizing the results in the literature with our mass and redshift intervals. However, we find significant field-to-field variations of the number densities up to a factor of 2–3, highlighting the effect of cosmic variance and suggesting the presence of overdensities of red quiescent galaxies at
z
> 3, as could be expected for highly clustered massive systems. Importantly, JWST enables the robust identification of quenching/quiescent galaxy candidates at lower masses and higher redshifts than before, challenging standard formation scenarios. All data products, including the literature compilation, are made publicly available.
We present new observations, carried out with IRAM NOEMA, of the atomic neutral carbon transitions C
I
(
3
P
1
–
3
P
0
) at 492 GHz and C
I
(
3
P
2
–
3
P
1
) at 809 GHz of GN20, a well-studied ...star-bursting galaxy at
z
= 4.05. The high luminosity line ratio C
I
(
3
P
2
–
3
P
1
) /C
I
(
3
P
1
–
3
P
0
) implies an excitation temperature of 48
+14
−9
K, which is significantly higher than the apparent dust temperature of
T
d
= 33 ± 2 K (
β
= 1.9) derived under the common assumption of an optically thin far-infrared dust emission, but fully consistent with
T
d
= 52 ± 5 K of a general opacity model where the optical depth (
τ
) reaches unity at a wavelength of
λ
0
= 170 ± 23
μ
m. Moreover, the general opacity solution returns a factor of ∼2× lower dust mass and, hence, a lower molecular gas mass for a fixed gas-to-dust ratio, than with the optically thin dust model. The derived properties of GN20 thus provide an appealing solution to the puzzling discovery of starbursts appearing colder than main-sequence galaxies above
z
> 2.5, in addition to a lower dust-to-stellar mass ratio that approaches the physical value predicted for starburst galaxies.
Abstract
We analyze a sample of 3300 galaxies between redshifts
z
≃ 3.5 and
z
≃ 8.5 selected from James Webb Space Telescope (JWST) images in the Hubble Ultra Deep Field and UKIDSS Ultra Deep Survey ...field, including objects with stellar masses as low as ≃10
8
M
⊙
up to
z
≃ 8. The depth and wavelength coverage of the JWST data allows us, for the first time, to derive robust stellar masses for such high-
z
, low stellar mass galaxies on an individual basis. We compute the galaxy stellar mass function, after complementing our sample with ancillary data from CANDELS to constrain the GMSF at high stellar masses (
M
>
M
*
). Our results show a steepening of the low stellar mass end slope (
α
) with redshift, with
α
= −1.61 ± 0.05 at
z
≃ 4 and
α
= −1.98 ± 0.14 at
z
≃ 7. We also observe an evolution of the normalization
ϕ
*
from
z
≃ 7 to
z
≃ 4, with
ϕ
z
≃
4
*
/
ϕ
z
≃
7
*
=
130
−
50
+
210
. Our study incorporates a novel method for the estimation of the Eddington bias, which takes into account its possible dependence both on stellar mass and redshift, while allowing for skewness in the error distribution. We finally compute the resulting cosmic stellar mass density and find a flatter evolution with redshift than previous studies.
ABSTRACT
We present a detailed study of a galaxy merger taking place at z = 1.89 in the GOODS-S field. Here, we analyse Keck/MOSFIRE spectroscopic observations from the MOSFIRE Deep Evolution Field ...(MOSDEF) survey along with multiwavelength photometry assembled by the 3D-HST survey. The combined data set is modelled to infer the past star formation histories (SFHs) of both merging galaxies. They are found to be massive, with log10(M*/M⊙) > 11, with a close mass ratio satisfying the typical major-merger definition. Additionally, in the context of delayed-τ models, GOODS-S 43114, and GOODS-S 43683 have similar SFHs and low star formation rates (log10(SFR(SED)/${\rm M}_{\odot }\,\rm {yr}^{-1}$) < 1.0) compared to their past averages. The best-fitting model SEDs show elevated H δA values for both galaxies, indicating that their stellar spectra are dominated by A-type stars, and that star formation peaked ∼0.5−1 Gyr ago and has recently declined. Additionally, based on SED fitting both merging galaxies turned on and shut off star formation within a few hundred Myr of each other, suggesting that their bursts of star formation may be linked. Combining the SFHs and H δA results with recent galaxy merger simulations, we infer that these galaxies have recently completed their first pericentric passage and are moving apart. Finally, the relatively low second velocity moment of GOODS-S 43114, given its stellar mass suggests a disc-like structure. However, including the geometry of the galaxy in the modelling does not completely resolve the discrepancy between the dynamical and stellar masses. Future work is needed to resolve this inconsistency in mass.
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